Intravitreal neovascularization is an important lesion that occurs in diabetic retinopathy and other related proliferative retinopathies which are recognized as major causes of blindness in the United States. An experimental model of intravitreal neovascularization has been successfully developed which is quite similar to that seen in human proliferative retinopathies. This experimental model enables us to carry out an extensive, in-depth study of biochemical changes and possible vasoproliferative factors that are involved. The primary goal is to isolate a vasoproliferative factor(s) and to develop an effective inhibitor(s) or pharmacologic agent(s) against the factor(s) and to elucidate the mechanism of vasoproliferation, with special emphasis on the role of lysosomes and the damage of vitreous-retinal boundary in the process of intravitreal neovascularization. Rabbit corneal micropockets and vascular endothelial cell cultures will be used as bioassay techniques.